1. Field of the Invention
The present invention relates to fibre channel systems, and more particularly, to extending physical fibre channel fabric capabilities using virtual fabrics.
2. Background of the Invention
Fibre channel is a set of American National Standard Institute (ANSI) standards, which provide a serial transmission protocol for storage and network protocols such as HIPPI, SCSI, IP, ATM and others. Fibre channel provides an input/output interface to meet the requirements of both channel and network users.
Fibre channel supports three different topologies: point-to-point, arbitrated loop and fibre channel fabric. The point-to-point topology attaches two devices directly. The arbitrated loop topology attaches devices in a loop.
The fibre channel fabric topology attaches host systems directly to a fabric, which are then connected to multiple devices. The fibre channel fabric topology allows several media types to be interconnected.
Fibre channel is a closed system that relies on multiple ports to exchange information on attributes and characteristics to determine if the ports can operate together. If the ports can work together, they define the criteria under which they communicate.
In fibre channel, a path is established between two nodes where the path's primary task is to transport data from one point to another at high speed with low latency, performing only simple error detection in hardware.
Fibre channel fabric devices include a node port or “N_Port” that manages fabric connections. The N_port establishes a connection to a fabric element (e.g., a switch) having a fabric port or F_port. Fabric elements include the intelligence to handle routing, error detection, recovery, and similar management functions.
A fibre channel switch is a multi-port device where each port manages a simple point-to-point connection between itself and its attached system. Each port can be attached to a server, peripheral, I/O subsystem, bridge, hub, router, or even another switch. A switch receives messages from one port and automatically routes it to another port. Multiple calls or data transfers happen concurrently through the multi-port fibre channel switch.
Fibre channel switches use memory buffers to hold frames received and sent across a network. Associated with these buffers are credits, which are the number of frames that a buffer can hold per fabric port.
Current fibre channel standards only allow 239 switches using a 24-bit addressing scheme. This can be limiting as networks grow in size and complexity.
One proposal has been to use virtual fabrics (also known as Virtual Storage Area Network (“VSAN”) that will allow a physical fibre channel fabric to be extended beyond the current 239-switch limitation.
Virtual fabrics divide a physical fabric into multiple virtual fabrics. Each virtual fabric has its own switch domain Id, N_Port logins, fabric routing and fabric services (for example, name servers). A port may be a part of more than one virtual fabric.
Although use of virtual fabrics is useful, conventional fibre channel switch elements are not designed to handle various issues that arise using the virtual fabrics, for example, hard zoning and fibre channel extension methods.
Therefore, what is required is a fibre channel switch element that can extend the capabilities of a fabric by using virtual fabrics.